refrifgeration line sizing

[airdocc]

Looking to get a fresh opinion. I am about ready for a melt down. Replaced failed compressor,repaired piping leaks and the new replacement compressor is tight and drawing double it amperage with limited charge and correct R22charge. Manufacture verified bad compressor.Verified no obstruction in the system.
I have a 5 ton split system for a server room application that has lost the compresssor, bad short to ground. In addition to this it had been pumping down. I had some sort of obstruction in the refrigeration circuit. It is clear now.
I have a two fold question.One is the piping sized correctly.We belive so do you? Second question is are their any way to remove the screen at the a coil metering device,fixed orfice york A coil. I dont think it can be removed. The unit has a 65' line set.The liquid line is 5/8" acr.The suction line is 1-1/8" acr both liq/suc piping have 6 elbows, short radius. The piping is run horizantal about 50' and has two vertical rises about 8, each.
The factory says the piping is oversized Our design engineer evaluated and think we are okay. The factory concern is the liquid line is allowing liquid to run back to the compressor since the liquid line is oversized in their calculation. Also the suction line velocity is to low with 1-1/8.

thanks

[coolwhip]

Sounds like the pipeing size is ok, you need a hard start kit and a liquid line solonoid. You should be able to remove the screen for cleaning or replacment.

[Andy Schoen]

Figure the equivalent length of 6 SR elbows as follows: 5/8" OD elbows: 6 ft, 1-1/8" OD elbows: 11 ft.

Based on 5 tons R-22, 100°F liquid and 40°F evaporator, I show the 5/8" OD liquid line to have a 1.1 psi pressure drop, 0.4°F equivalent temperature drop, 126 ft/min velocity.

The 1-1/8" OD suction line: 1.6 psi pressure drop, 1.1°F equivalent temperature drop, 1670 ft/min velocity.

You could have used a 1/2" OD liquid line here: 3.3 psi pressure drop, 1.2°F equivalent temperature drop, 203 ft/min velocity. Your 5/8" OD line, however, should not cause any problems, other than perhaps requiring a tad more refrigerant to charge the system.

Your suction line sizing is fine.

[Andy Schoen]

If you think you are flooding on startup due to pressure equalization during off cycle, consider installing a TEV (and hard start kit if necessary). Not only will you limit pressure equalization, you'll get better performance. ;) I'm assuming here the unit is piped in such a manner that liquid cannot make its way back to the compressor thru the condenser.

[absenceofheat]

Go Andy Go

[emmettair]

I'm a little confused, are you saying the new compressor you just installed is drawing double the rated rla? When you mentioned limited charge, do you mean load? Need to know the basics. You said you have a correct ref. charge, by superheat? What is your superheat? What are your pressures? Temp. drop across evap.? What type of compressor-recip. or scroll? Is there an oil sight glass, if so whats the oil level on startup and after some run time? Any foaming or washout? Crankcase heater? As for the piping sizes, i would think there a size too large, but thats not a big deal. I see another member has done the calculations so you should be ok. Traps on your risers? On that 50' horizontal run, is the suction line pitched properly? Did you install burnout cores/drier after compressor replacement? If so, did you replace them with standards after a few days? Being that its for a server room, i assume it runs year-round, what type of head pressure control? As for the screen, not sure, but if you think its a problem, the answers to some of the above questions will tell ya. Sorry if i got off track here, i know your question was only 2 fold-just trying to help.

[The Doctor]

Looking to get a fresh opinion. I am about ready for a melt down. Replaced failed compressor,repaired piping leaks and the new replacement compressor is tight and drawing double it amperage with limited charge and correct R22charge. Manufacture verified bad compressor.Verified no obstruction in the system.
I have a 5 ton split system for a server room application that has lost the compresssor, bad short to ground. In addition to this it had been pumping down. I had some sort of obstruction in the refrigeration circuit. It is clear now.
I have a two fold question.One is the piping sized correctly.We belive so do you? Second question is are their any way to remove the screen at the a coil metering device,fixed orfice york A coil. I dont think it can be removed. The unit has a 65' line set.The liquid line is 5/8" acr.The suction line is 1-1/8" acr both liq/suc piping have 6 elbows, short radius. The piping is run horizantal about 50' and has two vertical rises about 8, each.
The factory says the piping is oversized Our design engineer evaluated and think we are okay. The factory concern is the liquid line is allowing liquid to run back to the compressor since the liquid line is oversized in their calculation. Also the suction line velocity is to low with 1-1/8.

thanks
I will pose this in the form of a question, so please overlook any unintended tone of sarcasm. Is 1 1/8" on a 5 ton ever oversized? I would not think so. It is a knee-jerk answer, so you can take it with a grain...should be okay there though.
Refrigerant migration is temperature-related, is it not. Is there extra crankcase heaters on this pig? I recently installed york's vfd on two 15ton circuits, and it included a 2nd CCH for each pig. just food for thought on refrigerant migration in the off-cycle.
Sorry don't know york's screen set-up. in many instances I know of installing a filter-drier before the screen and punching out the screen, but ...that's not my advice to you, just relying on the F/D to do the work after lineset is clear.

[hvaccop]

Make sure you have crankcase heaters and a 24 v solenoid on liquid line at Air Handler. Wire y and c to solenoid. Also be careful you are not getting the "hydrolic hammer" effect with the large liquid line. Basically it means there is too much charge in system, to compensate for a large liquid line, for the compressor to handle, when the compressor starts it creates such a force in compressor shell and condensor. Bad things happen.. Especially critical on long line sets. I had a commercial contract where carrier was installed by another contractor. Lost 4 compressor and 3 condensor coils in 3 years. The problem was the "hydrolic hammer" effect and the long line sets with no solenoids and liquid lines too big. Made necessary changes and no problems in a long time

[bertoh]

afixed orfice coil is same as a capillary tube system. these systems are charged by subcooling based on OAT. i am pretty sure they are limited to how low OAT they can run at. the answers to both of those questions should be with the IOM.1 1/8 " suction on a 5 ton is standard on a resi unit but probably upto 25 ft. andy schoen has the math done on it. i assume two 8ft. risers means a total of 16 ft. rise? is the comp above the evap? you may have oil return problem. risers should be down sized to make vapour travel at 4000 fpm in the risers. traps? the fixed orfice can be changed if clogged. i hope you used nitrogen fixing those leaks or their will be more pumping down.
i would suggest a txv and (pumpdown solenoid at evap) also head pressure control and possibly receiver depending on how low OAT goes in your area.
dont get what you are saying about twice the amperage. twice other comp, twice RLA?

[MANSON]

Have not seen the basics anywhere in your post: Pressures, superheat, subcooling, evaporator delta T. When taking your superheat reading, take it at the compressor to ensure that you are sufficiently cooling it with the refrigerant due to such a long line set. Lack of airflow will kill a compressor (I like 144 sq inches per ton for R/A and make sure you are moving 400 cfm per ton). Server rooms must be cooled year round, no mention of hot gas bypass and condenser fan cycling switch or motor master. Liquid line solenoid is a good idea and make sure the crankcase heater is working. What about humidity control and reheat? Just some things to look at. Good luck!!

[grendil]

Looking to get a fresh opinion. I am about ready for a melt down. Replaced failed compressor,repaired piping leaks and the new replacement compressor is tight and drawing double it amperage with limited charge and correct R22charge. Manufacture verified bad compressor.Verified no obstruction in the system.
I have a 5 ton split system for a server room application that has lost the compresssor, bad short to ground. In addition to this it had been pumping down. I had some sort of obstruction in the refrigeration circuit. It is clear now.
I have a two fold question.One is the piping sized correctly.We belive so do you? Second question is are their any way to remove the screen at the a coil metering device,fixed orfice york A coil. I dont think it can be removed. The unit has a 65' line set.The liquid line is 5/8" acr.The suction line is 1-1/8" acr both liq/suc piping have 6 elbows, short radius. The piping is run horizantal about 50' and has two vertical rises about 8, each.
The factory says the piping is oversized Our design engineer evaluated and think we are okay. The factory concern is the liquid line is allowing liquid to run back to the compressor since the liquid line is oversized in their calculation. Also the suction line velocity is to low with 1-1/8.

thanks

Your Liquid Line is oversized, 3/8. Set up a Pump Down Solenoid, even consider a Accumulator.

[Andy Schoen]

Your Liquid Line is oversized, 3/8. Set up a Pump Down Solenoid, even consider a Accumulator.
3/8" OD is too small, given 71 equivalent feet of liquid line. I figure 16 psi pressure drop, or about a 5.7°F equivalent temperature drop. 1/2" OD would be normally selected for this application.

Your other suggestions are on target. :cool:

[grendil]

3/8" OD is too small, given 71 equivalent feet of liquid line. I figure 16 psi pressure drop, or about a 5.7°F equivalent temperature drop. 1/2" OD would be normally selected for this application.

Your other suggestions are on target. :cool:

Respectfully disaggree, Even in Long line sizing manufacturers suggest 3/8" LL.
5 ton is small no need to go to 1/2". Line lenght is short also. Tooo much charge...:)

[Andy Schoen]

Respectfully disaggree, Even in Long line sizing manufacturers suggest 3/8" LL.
Line lenght is short also.
71 equivalent feet is short? :confused:

[grendil]

71 equivalent feet is short? :confused:

Sure I wouldn't say it's a long line application. Check out York or Carrier sizing, read the Bold letters about the common mistake of LL sizing on small tonage under 7.5 Tons.

[Davester]

While a 3/8" LL will have greater pressure drop than the 5/8", it shouldn't be enough to cause any problems with a TXV (aka TEV).

But, I'm not so sure about a fixed orifice with long line at low ambient.
Seems to me that might be "impossible" to charge correctly without floodback under some operating conditions. If the compressor is below the evaporator, all that hot liquid in the line could even drain back through the condenser to the compressor discharge... what will happen when the compressor starts with "no" gas volume at the top of the condenser? (Not good!)

Just my 2 cents worth, but I'd put a York TXV kit on that coil and go with the factory recommended line size.

[spongebrain~~]

Hey guys................what would you recomend for reading on the subject of load calculations, installing and designing split systems? I,ve been doing resi service for a little while, but I want to learn more about installing. I need to start studying manuals J and D, but what else would help me?

[hvacinstallation]

5/8 does seem big and overcharge is possibe. 2 8' rises with a burnout, I would definately consider the need for a P-trap if the compressor is on the roof, I don't think you specified. If your not the installing contractor, you may consider changing the liquid line to 1/2ACR while the system is recovered. Also make sure the filter/dryers are changed obviously. Is there a hot gas line and make sure it is not insulated?

[kelvin]

hey Doc you're not responding to give us more information about this problem. Subcooling, superheat, etc? Is this a 3 phase or a single phase system. I don't understand why would you double your RLA if you oversize your pipe a little. More data needed. :confused: :confused: :confused:

[pecmsg]

Respectfully disaggree, Even in Long line sizing manufacturers suggest 3/8" LL.
5 ton is small no need to go to 1/2". Line lenght is short also. Tooo much charge...:)

Grendil

Do a search on Mr Andy Schoen. Then you can post an apology.:D

[hvacinstallation]

Have you installed a P-Trap on the suction for you 16 feet of vertical rise if the compressor is on the roof.

If the compressor is in the space, you should have inverted traps on the liquid and suction if the compressor is in the space and condensor is on the roof (as in a liebert) system.

Have you resorted to reading the manual yet?

[vmc1161]

Did you liquid charge into the suction line...maybe before you started the compressor? You can make a mess out of the compressor by charging too fast or overcharging...good luck...oh you are sure it is the right comp and voltage...:eek:

Oh, long line starts at 50 equivalent feet...I would stay with 3/8 for that run.


.

[Andy Schoen]

Grendil

Do a search on Mr Andy Schoen. Then you can post an apology.:D


I'm most proud of the plays I've produced for shortbridge theatre company. :D http://shortbridge.tripod.com/shortbridge/id1.html

Or I may have found a 4th cousin once removed... :o

[airdocc]

Sorry I have been burning the midnight oil taking care of my daughter she been very sick and haven't had a chance to reply to questions.VMc1161 I weighed in the charge in the liquid line. Weighing in the charge to the suction side is like smoking in the dynamite shed .
I sent the compressor back to the factory.They have determined the compressor had a manufacturing defect.
I also manually measured the line set and weighed in the charge. Installed traps an a accumalator with lq & suc line driers with manual L.P. pressure switch and crankcase heater. Installed ECM fan controller with a ball bearing motor.I agree I would feel a whole lot better with a 3/8" liquid line.My other concern is on the off cycle the 5/8" liquid refrigerent stack up the riser and fills the compressor with liquid .Customer wouldn't approve solonoid valve for Liquid line.
Once I had operating conditions I was able to evaluate system operation.I have concluded the system has major design flaws.The computer room has a raised floor with one down flow air handler that discharges cool air below the floor and and one up flow air handler.The upflow air handler has a 20X20 plenum with supply air registers that blow air on to the face of the server racks glass doors and of course they are closed.The server racks are closed and allow no air flow from the front.The rack is designed to pull air up from a perferated floor tile.Then the rack fan located on the top of the rack is able to pull the cool air from the floor tile up through the computers to the top of the rack where it discharges the hot air from the computers. And of course their in no perfarated floor tile below the rack therfore allowing no cool air up through thr server rack.The return for this air handler unit is located at the bottom of the unit above the floor 2 inches. the thermostat are located in the incorrect zone and to not aquire the actual temperature of the the correct zone.The return air to the up flow air handler is 60 to 62 F.Big problem.Pointed this out to the customer and the IT guy It guy says this is a non issue.My understanding from a employee this has been a problem for several years. Have grace I probably missed something in this post but my kids are screaming in the back round and I have to go.

Thanks for the help.

Doc

[BigJon3475]

Accumulator should be able to hold entire charge. Floodback dilutes the compressors oil with liquid ref. and causes foaming in the crankcase. When liquid is in the bottom of the accumulator and is being vaporized high compression amperage draws may occur because it see a dense saturated or near saturated coming into it and being compressed. There will be little or no superheat to the vapor coming off the liquid in the accumulator. This causes high mass flow rates of ref. and can overload a compressor to the point of overheating.
During the off cycle, the accumulator may have some liquid ref. move back into it by gravity from the evap. and suc. line, especially when the system does not have an automatic pump down for it's off cycles. The liquid ref will flow the the liquid ref. and oil return metering device and seeks its own level both inside an outside the u tube formation of the suction piping of the accumulator. This means that the utube of suction piping inside the accum. will have a column of liquid ref in it during the off cycle simply because it seeks its own level. This column will be sucked out of the accum. if it weren't for a a pressure equalization orifice at the outlet of the accum. It will equalize pressures on both sides of the liquid column when the compressor is on or off. This will prevent liquid from being sucked out of the u tube of the accum. and possibly damaging the compressor. The liquid column will momentarily hang in the column and rapidly vaporize on compressor startup. This is the time where sat. gas can enter the comp. Once the column of vapor is cleared or vaporized the compressor will then begin to see superheated gas.
The accumulator should have adequate liquid holding capacity. This should be 50% of the entire system charge. The accumulator should not add excessive pressure drop to the system. Don't base the accumulator on the size of the piping.

[airdocc]

Thanks good information. I sized the acumaltor taking in to account the total charge for the system.
Thanks
Doc

[rolo]

Very simple classic case of excesive oil pressure. Get an accurate liquid filled gage and read your PSI, then bleed as necessary. Amperage will decrease.

[airdocc]

Not sure I agree. The factory concluded the original replacement compressor was defective. The internal clearance was too tight.I removed the compressor that was drawing excesive amps and installed new warrenty replacement compressor. Normal amp draw and super heat and sub cooling are present at this time. Temeprature drop is okay, due to increasing set point of the down flow unit that was causing low entering retun air temperatures. I have the air handler that had the failed compressor maintaining the room set point at 72.F and the second air handler/condensing unit set as emergency back up with a set point of 76 F untill other issues listed in my post above are approved for resolution. The room is maintaining at this point.

thanks
Doc